Method and system for maintaining a gnss receiver in a hot-start state

ABSTRACT

Aspects of a method and system for maintaining a GNSS receiver in a hot-start state are provided. A GNSS receiver in a standby mode may transition from a sleep state to a wakeup state to acquire ephemeris from, for example, GPS signals, GALILEO signals, and/or GLONASS signals. The acquired ephemeris may be stored and utilized for the GNSS receiver to generate a navigation solution in a normal mode. The GNSS receiver may transition from the normal mode to the sleep state or the wakeup state in standby mode. A sleep period and a wakeup period for the full sleep-wakeup cycle in the standby mode may be predetermined or dynamically adjusted based on required QoS, quality of satellite signals, and/or user inputs. The sleep period and the wakeup period may be selected in a way to ensure a valid and complete ephemeris to be acquired.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

Not applicable

FIELD OF THE INVENTION

Certain embodiments of the invention relate to signal processing forcommunication systems. More specifically, certain embodiments of theinvention relate to a method and system for maintaining a GNSS receiverin a hot-start state.

BACKGROUND OF THE INVENTION

A Global Navigation Satellite System (GNSS) such as the GlobalPositioning System (GPS) comprises a collection of twenty-fourearth-orbiting satellites. Each of the GPS satellites travels in aprecise orbit about 11,000 miles above the earth's surface. A GPSreceiver locks onto at least three of the satellites to determine itsposition fix. Each satellite transmits a signal, which is modulated witha unique pseudo-noise (PN) code, at the same frequency. The GPS receiverreceives a signal that is a mixture of the transmissions of thesatellites that are visible to the receiver. The GPS receiver detectsthe transmission of a particular satellite based on corresponding PNcode. For example, by correlating the received signal with shiftedversions of the PN code for that satellite in order to identify thesource satellite for the received signal and achieve synchronizationwith subsequent transmissions from the identified satellite.

When the GPS receiver is powered up, it steps through a sequence ofstates until it can initially determine a navigation solution comprisingposition, velocity and time. Afterwards, the satellite signals aretracked continuously and the position is calculated periodically.Precise orbital information, known as ephemeris or ephemeris data,transmitted by each satellite is used in calculating the navigationsolution. Ephemeris or ephemeris data for a particular satellite may bedecoded from orbit data once the GPS signal has been acquired. Eachsatellite broadcasts its own ephemeris data, the broadcast lasts for 18seconds, repeating every 30 seconds.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY OF THE INVENTION

A method and/or system for maintaining a GNSS receiver in a hot-startstate, substantially as shown in and/or described in connection with atleast one of the figures, as set forth more completely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram illustrating an exemplary GNSS satellite navigationsystem operable to maintain a GNSS receiver in a hot-start state, inaccordance with an embodiment of the invention.

FIG. 2 is a state diagram illustrating an exemplary GNSS receiveroperation that enables the GNSS receiver to be maintained in a hot-startstate, in accordance with an embodiment of the invention.

FIG. 3 is a diagram illustrating an exemplary GNSS enabled devicecomprising a GNSS receiver operable to be maintained in a hot-startstate, in accordance with an embodiment of the invention.

FIG. 4 is a flow chart illustrating exemplary steps for maintaining aGNSS receiver in a hot-start state, in accordance with an embodiment ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention may be found in a method and systemfor maintaining a GNSS receiver in a hot-start state. Various aspects ofthe invention may enable a GNSS enabled handset to operate in a normalmode and a standby mode. In the standby mode, the GNSS enabled handsetmay be configured to switch periodically or aperiodically between asleep state in the standby mode and a wakeup state in the standby mode.For example, the GNSS enabled handset in the standby mode may beconfigured to transition from the sleep state in the standby mode to thewakeup state in the standby mode. In the wakeup state of the standbymode, the GNSS enabled handset may enable turning on corresponding GNSSfront end to track satellite signals and acquire fresh navigationinformation such as fresh ephemeris from the satellite signals. Theacquired fresh ephemeris may be stored and may be used for futurestart-ups of the GNSS enabled handset to generate a navigation solutionin the normal mode. The satellites signals may comprise GPS signals,GALILEO signals, and/or GLONASS signals. The GNSS enabled handset mayoperate in various ways. For example, after the start-up for variousoperations in the normal mode, the GNSS enabled handset may beconfigured to return to either the sleep state or the wakeup state fromthe normal mode, or just stay in the normal mode. A sleep period of thesleep state and a wakeup period of the wakeup state may be predeterminedor may be dynamically adjusted. The sleep period and the wakeup periodmay be determined based on QoS, quality of satellite signals, and/oruser inputs. To generate a navigation solution for the GNSS enabledhandset, the fresh ephemeris may be acquired after the GNSS enabledhandset transitions from the sleep state in the standby mode to thewakeup state in the standby mode, and may be utilized. Accordingly, thesleep period may be chosen such that it is less than a period at whichthe fresh ephemeris is changed by one or more satellites, and the wakeupperiod may be chosen so that it is long enough to enable collection ofthe fresh ephemeris.

FIG. 1 is a diagram illustrating an exemplary GNSS satellite navigationsystem operable to maintain a GNSS receiver in a hot-start state, inaccordance with an embodiment of the invention. Referring to FIG. 1,there is shown a GNSS satellite navigation system 100, comprising a GNSSenabled handset 110, of which a GNSS enabled cell phone 140 a, a GNSSenabled smartphone 140 b, and a GNSS enabled laptop 140 c are presented,a plurality of GNSS satellites 120 a-120 c, and a wireless communicationnetwork 130.

The GNSS enabled handset 110 may comprise suitable logic circuitryand/or code that may be to receive satellite broadcast signals from theGNSS satellites 120 a-120 c to determine a position fix of the GNSSenabled handset 110. The GNSS enabled handset 110 may be capable oftransmitting and/or receiving radio signals via the wirelesscommunication network 130, which may be compliant with, for example,3GPP, 3GPP2, WiFi, and/or WiMAX communication standards. The GNSSenabled handset 110 may support various operating modes such as, forexample, a normal mode (high power) and a standby mode (lower power), toaccomplish different tasks during the process of acquiring andmaintaining the GNSS information.

The normal mode may comprise a mode in which the GNSS enabled handset110 operates at its normal current consumption level to support its mainsystem CPU to run all main functions normally. In the normal mode, theGNSS enabled handset 110 may utilize a high speed clock that consumermore power than a low speed clock that may be utilized for the standbymode.

The standby mode may comprise a mode in which the GNSS enabled handset110 operates at it's a low current consumption level. For example, inthe standby mode, the GNSS enabled handset 110 may operate at alow-power level to monitor and activate bus activity. In the standbymode, the GNSS enabled handset 110 may be configured to turn off mainfunctions that depend on its main system CPU. In this regard, the GNSSenabled handset 110 in the standby mode may utilize a low frequencyclock rather than a high frequency clock that is utilized in the normalmode.

In the standby mode, the GNSS enable handset 110 turns off correspondingradio components required for transmitting and/or receiving data via thewireless communication network 130. However, the GNSS enabled handset110 may be configured to turn on or off radio components related toreceiving GNSS data as needed. The GNSS enabled handset 110 in thestandby mode may be in a wakeup state or a sleep state. The wakeup statein the standby mode corresponds to the situation that the GNSS enabledhandset 110 is in the standby mode and is capable of receiving GNSSdata. The sleep state in the standby mode corresponds to the situationwhere the GNSS enabled handset 110 is in the standby mode and is notcapable if receiving GNSS data.

Depending on the knowledge of the GNSS information such as last GNSSposition, current GNSS time and/or ephemeris data, the GNSS enabledhandset 110 may apply different strategies for GNSS start-up, forexample, a cold-start, a warm-start, or a hot-start, in acquiring GNSSinformation. In this regard, in a standby mode, the GNSS enabled handset110 may be configured to maintain the GNSS information in a hot-startstate by periodically waking up and running long enough to decode freshephemeris. The decoded fresh ephemeris may be used in subsequentstartups to improve the time to first fix (TTFF) for the GNSS enabledhandset 110.

The GNSS satellites 120 a-120 c may comprise suitable logic, circuitryand/or code that may be enabled to generate and broadcast suitableradio-frequency signals. The broadcast RF signals may comprise variousnavigation information such as orbital information, known as ephemerisor ephemeris data. The orbital information may comprise orbital locationas a function of GNSS time. The broadcast ephemeris may change every twohours at the GNSS satellites 120 a-120 c and may be valid for aparticular period of time into the future, for example, four hours. Thebroadcast ephemeris may be received and decoded by a GNSS satellitereceiver, which may be integrated in the GNSS enabled handset 110. Thebroadcast ephemeris may be utilized to determine a navigation solutionsuch as, for example, position, velocity, and clock information of theGNSS enabled handset 110.

The wireless communication network 130 may comprise suitable logic,circuitry and/or code that may be enabled to provide various voiceand/or data services via CDMA 2000, WCDMA, GSM, UMTS, WiFi, or WiMAXcommunication standards.

In operation, the GNSS enabled handset 110 may be enabled to receivesatellite broadcast signals from the GNSS satellites 120 a-120 c todetermine a navigation solution such as a position fix of the GNSSenabled handset 110. A sequence of states may be executed to acquire andmaintain the GNSS navigation information such as ephemeris in order tocalculate the navigation solution for the GNSS enabled handset 110. Forexample, in a standby mode, the GNSS enabled handset 110 may be enabledto maintain ephemeris in a hot-start state by periodically waking up toacquire GNSS broadcast signals from the GNSS satellites 120 a-120 c andrunning long enough to decode ephemeris. The fresh ephemeris may be usedin subsequent startups to improve the time to first fix (TTFF) of theGNSS enabled handset 110. The determined navigation solution may be usedfor various location based services via the GNSS enabled handset 110and/or the wireless communication network 130.

FIG. 2 is a state diagram illustrating an exemplary GNSS receiveroperation that enables the GNSS receiver to be maintained in a hot-startstate, in accordance with an embodiment of the invention. Referring toFIG. 2, there is shown an exemplary operation state machine comprising anormal mode 210 and a standby mode 220. The standby mode 220 maycomprise a sleep state 222 and a wakeup state 224.

In the normal mode 210, the GNSS enabled handset 110 may be fullypowered to perform the functions of GNSS signal search, acquisition,measurement and satellite tracking. The period of a full operating cyclefor the normal mode 210 may be software adjustable. The GNSS enabledhandset 110 in the normal mode 210 may output position information at auser-defined rate. Depending on implementation, the GNSS enabled handset110 may be configured to switch automatically between the standby mode220 and the normal mode 210 to save power, or just stay in the normalmode after being switched from the standby mode. In the standby mode220, the GNSS enabled handset 110 may be operating at minimal power,which may be significantly less than in the normal mode 210. In thisregard, in the standby mode 220, the GNSS enabled handset 110 may beconfigured in the sleep state 222 or in the wakeup state 224. In thesleep state 222, the GNSS enabled handset 110 may be configured to turnoff GNSS RF components to save power consumption.

The GNSS enabled handset 110 may be configured to periodically wake upand enter the wakeup state 224 from the sleep state 222 to acquire freshephemeris with lower power consumption. The ephemeris may change everytwo hours at satellites such as the GNSS satellites 120 a-120 c, and maybe good for 4 hours. An appropriate wake up interval of, for example,every two hours, may be utilized. In the wakeup state 224, the GNSSenabled handset 110 may acquire ephemeris and maintain GNSS navigationinformation without being fully powered. For example, the GNSS enabledhandset 110 may wake up without even turning on user interfacecomponents such as the display. During the wakeup state 224, the GNSSenabled handset 110 may stay on long enough to acquire a completeephemeris. The GNSS enabled handset 110 may consume a small amount ofbattery power for various operations during the wakeup state 224. TheGNSS enabled handset 110 may store the acquired ephemeris data toprovide the fresh ephemeris for GNSS start-up to, for example, calculatea navigation solution or perform navigation update in the normal mode210. The GNSS enabled handset 110 may return to the sleep state 222 orthe wakeup state 224 in the standby mode 220 after the navigationupdate. Depending on implementation, the GNSS enabled handset 110 maystay in the normal mode after the navigation update. The period of afull sleep-wakeup cycle in the standby mode may be software adjustablevia various timing control. For example, the GNSS enabled handset 110may be configured via setting up a wakeup timer and/or a sleep timer forupdating navigation information of the GNSS enabled handset 110. Thewakeup timer and/or the sleep timer may be pre-determined and/or may beadjusted depending on, for example, required QoS and/or quality of theacquired ephemeris data.

FIG. 3 is a diagram illustrating an exemplary GNSS enabled devicecomprising a GNSS receiver operable to be maintained in a hot-startstate, in accordance with an embodiment of the invention. Referring toFIG. 3, there is shown the GNSS enabled handset 110 comprising anantenna 302, a GNSS front end 304 a, a telecommunication front end 304b, a processor 306, a memory 308, and a user interface 310.

The antenna 302 may comprise suitable logic, circuitry and/or code thatmay be enabled to receive L band signals from the plurality of GNSSsatellites 120 a-120 c. The antenna 302 may be enable transmissionand/or reception of radio signals via, for example, a 3G radiocommunication system, for communications among 3G devices.

The GNSS front end 304 a may comprise suitable logic, circuitry and/orcode that may be enabled to receive GNSS satellite broadcast signals viathe antenna 302 and convert them to GNSS baseband signals for furtherbaseband signal processing in the processor 306.

The front end 304 b may comprise suitable logic, circuitry and/or codethat may be enabled to transmit and/or receive radio frequency (RF)signals via a telecommunication network such as the wirelesscommunication network 130 via the antenna 302. The front end 304 b mayenable conversion of the received RF signals to corresponding basebandsignals, which may be suitable for further baseband signal processing inthe processor 306.

The processor 306 may comprise suitable logic, circuitry and/or codethat may be enabled to process received satellite signals as well assignals received from the wireless communication network 130. Theprocessor 306 may be configured to extract navigational information fromreceived satellite signals. The extracted navigation information may beutilized to determine navigational information such as a position fixfor the GNSS enabled handset 110. The processor 306 may be programmed toturn on or off the GNSS front end 304 a. For example, the processor 306may periodically enter the standby mode 220 in which the GNSS front end304 a is turned on and information such as ephemeris from the GNSSsatellites 120 a-120 c may be received. The processor 306 may enable theGNSS enabled handset 110 to operate by consuming a minimal amount ofpower during the wakeup state 224. For example, in the standby mode 220,the processor 306 may periodically wake up the GNSS front end 304 a forreceiving GNSS signals, extract, and store information such as ephemerisfrom the received GNSS signals without even turning on the display orother circuitry in the GNSS enabled handset 110 that is not required toenable receiving of the information. In instances when a navigationupdate may be required, for example, via the user interface 310 or viavarious upper layer applications from the wireless communication network130, the processor 306 may provide the fresh ephemeris stored in thememory 308 for use.

The memory 308 may comprise suitable logic, circuitry, and/or code thatmay enable storing of information such as executable instructions anddata that may be utilized by the processor 306. The executableinstructions may comprise algorithms that may be applied to extractephemeris from received GNSS broadcast navigation signals and tocalculate a navigation solution from the extracted ephemeris. The datamay comprise GNSS navigation information such as the extracted freshephemeris. The memory 308 may comprise RAM, ROM, low latency nonvolatilememory such as flash memory and/or other suitable electronic datastorage.

The user interface 310 may comprise suitable logic, circuitry, and/orcode that may enable presentation of navigation information. Thenavigation information may be presented graphically, aurally, inresponse to user input requests for a navigation update via, forexample, a keyboard, a keypad, a thumbwheel, a mouse, touchscreen,audio, a trackball and/or other input method.

In operation, a plurality of radio signals may be received at theantenna 302 coupled to the GNSS enabled handset 110. The receivedplurality of radio signals may be communicated to the GNSS front end 304a or the telecommunication front end 304 b, respectively, depending onthe type of received radio signals. When the GNSS enabled handset 110may be in the standby mode 220, the processor 306 may be enabled toswitch the GNSS enabled handset 110 between the sleep state 222 and thewakeup state 224 periodically to save power. The wakeup state 224 mayallow the processor 306 to wake up the GNSS front end 304 a forreceiving GNSS signals and to acquire navigation information such asephemeris from the GNSS satellites 120 a-120 c by using a small amountof power. In the wakeup state 224, the processor 306 may be enabled toextract complete ephemeris from the received GNSS signals, and store theextracted ephemeris in the memory 308, accordingly. Various operationssuch as, for example, acquiring fresh navigation information from thesatellite signals in the wakeup state 224 may be executed without eventurning on the user interface 310 to save power. When a navigationupdate may be needed, the processor 306 may use the latest ephemerisstored in the memory 308 to generate a navigation solution.

FIG. 4 is a flow chart illustrating exemplary steps for maintaining aGNSS receiver in a hot-start state, in accordance with an embodiment ofthe invention. Referring to FIG. 4, the exemplary steps start with thestep 402. It is assumed that the GNSS enabled handset 110 may start inthe standby mode 220. In step 402, the GNSS enabled handset 110 mayselect a sleep interval and a wake-up interval. The sleep interval andthe wakeup interval may be predetermined or dynamically adjusted basedon one or more factors comprising QoS, quality of the satellite signals,battery life, and user input. In addition, a sleep timer and a wakeuptimer may be reset. The sleep timer and the wakeup timer may be used fortiming control of the full sleep-wakeup cycle.

In step 404, it may be determined whether the GNSS enabled handset 110may be in the sleep state 222. In instances where the GNSS enabledhandset 110 may be in the sleep state 222, then, in step 406, it may bedetermined whether the sleep timer has expired and there may besufficient battery life remained. In instances where the sleep timer mayexpire, then in step 408, the GNSS enabled handset 110 may wake up fromthe sleep state 224 and reset the awakening timer. In step 410, the GNSSenabled handset 110 may acquire GNSS navigation signals, acquire/decodea complete ephemeris from acquired GNSS navigation signals, and storethe fresh ephemeris into the memory 308. In step 412, determine if thewake up timer has expired, in instances where the wakeup timer mayexpire, then in step 414, the GNSS enabled handset 110 may enter intothe sleep state 222 and reset the sleep timer, then return to the step406. In step 404, in instances where the GNSS enabled handset 110 maynot be in the sleep state 222, the next step is step 410.

In step 406, in instances where the sleep timer has not expired and/orthere may be no sufficient battery life remained, and then executionremains in step 406. In step 412, in instances where the wakeup timerhas not expired, then the next step is step 410. The GNSS enabledhandset 110 may be switched from the standby mode 220 (step 402) to thenormal mode 210 for a navigation update. In step 416, it may bedetermined whether a navigation update is requested. In instances wherethe GNSS enabled handset 110 may request navigation information, then instep 418, the GNSS enabled handset 110 may enter the normal mode 210. Instep 420, the processor 306 may access the memory 308 for the freshephemeris to determine the requested navigation information. The GNSSenabled handset 110 may then enter the sleep state 222. Depending onimplementation and/or QoS requirements, the GNSS enabled handset 110 maybe configured to return to the wakeup state 224 in the standby mode fromthe normal mode 210, or stay in the normal mode 210 after performing thenavigation solution.

Aspects of a method and system for maintaining a GNSS receiver in ahot-start state are provided. In accordance with various embodiments ofthe invention, a navigation satellite system receiver such as the GNSSenabled handset 110 may operate in the normal mode 210 and the standbymode 220. In the standby mode 220, the GNSS enabled handset 110 may beconfigured to switch periodically or aperiodically between the sleepstate 222 and the wakeup state 224. For example, the GNSS enabledhandset 110 in the standby mode 220 may be enabled to transition fromthe sleep state 222 in the standby mode 220 to the wakeup state 224 inthe standby mode 220. In the wakeup state 224, the processor 306 mayturn on the GNSS front end 304 a to track satellite signals and acquirefresh navigation information such as fresh ephemeris from the satellitesignals. The acquired fresh navigation information comprising freshephemeris may be stored in the memory 308 and may be used to provide fora start-up of the GNSS enabled handset 110. The GNSS enabled device 110may utilize the fresh navigation information to generate a navigationsolution in the normal mode 210. After acquiring fresh ephemeris in thestandby mode 220, the GNSS enabled handset 110 may transition from thewakeup state 224 in the standby mode 220 back to the sleep state 222 inthe standby mode 220. The satellite signals may be GPS signals, GALILEOsignals, and/or GLONASS signals.

The GNSS enabled handset 110 may be implemented, such that after thestart-up for various operations in the normal mode 210, the GNSS enabledhandset 110 may be configured to return to either the sleep state 222 inthe standby mode 220 or the wakeup state 224 in the standby mode 220, orjust stay in the normal mode 210. A sleep period of the sleep state 222in the standby mode 220 and a wakeup period of the wakeup state 224 inthe standby mode 220 may be predetermined or may be dynamicallyadjusted. The sleep period in the standby mode 220 and the wakeup periodin the standby mode 220 may be determined based on exemplary factorscomprising QoS, quality of satellite signals, and/or user inputs. Thesleep period in the standby mode 220 may be selected or chosen so thatit is less than a period at which said fresh ephemeris is changed by oneor more satellites. The wakeup period in the standby mode 220 may beselected so that it is long enough for a period required for collectionof the fresh ephemeris.

Another embodiment of the invention may provide a machine and/orcomputer readable storage and/or medium, having stored thereon, amachine code and/or a computer program having at least one code sectionexecutable by a machine and/or a computer, thereby causing the machineand/or computer to perform the steps as described herein for maintaininga GNSS receiver in a hot-start state.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputer system, or in a distributed fashion where different elementsare spread across several interconnected computer systems. Any kind ofcomputer system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computer system with a computerprogram that, when being loaded and executed, controls the computersystem such that it carries out the methods described herein.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

1. A method for satellite communication, the method comprising: when anavigation satellite system receiver is in a sleep state during astandby mode, transitioning from said sleep state to a wakeup stateduring said standby mode to acquire fresh ephemeris; and when saidnavigation satellite system receiver subsequently transitions from saidstandby mode to a normal mode of operation, determining navigationinformation utilizing said acquired fresh ephemeris.
 2. The methodaccording to claim 1, comprising transitioning from said wakeup stateback to said sleep state in said standby mode, subsequent to saidacquisition of said fresh ephemeris.
 3. The method according to claim 1,wherein said fresh ephemeris is acquired from GPS signals, GLONASSsignals, and/or Galileo signals.
 4. The method according to claim 1,comprising storing said acquired fresh ephemeris in said navigationsatellite system receiver.
 5. The method according to claim 1,comprising returning to said sleep state in said standby mode from saidnormal mode of operation.
 6. The method according to claim 1, comprisingreturning to said wakeup state in said standby mode from said normalmode of operation.
 7. The method according to claim 1, comprisingstaying in said normal mode of operation after said transition from saidstandby mode to said normal mode of operation.
 8. The method accordingto claim 1, wherein, for said standby mode, a sleep period of said sleepstate and a wakeup period of said wakeup state are predetermined ordynamically adjusted.
 9. The method according to claim 8, wherein saidsleep period of said sleep state and said wakeup period of said wakeupstate are determined based on QoS, quality of said acquired freshephemeris, and/or user inputs.
 10. The method according to claim 8,wherein said sleep period of said sleep state is less than a period atwhich said fresh ephemeris is changed by one or more satellites.
 11. Themethod according to claim 8, wherein said wakeup period of said wakeupstate is greater than or equal to a period required for collection ofsaid fresh ephemeris.
 12. A system for satellite communication, thesystem comprising: one or more circuits for use in a navigationsatellite system receiver, wherein when said navigation satellite systemreceiver is in a sleep state during a standby mode, said one or morecircuits are operable to enable transition from said sleep state to awakeup state during said standby mode to acquire fresh ephemeris; andsaid one or more circuits are operable to determine navigationinformation utilizing said acquired fresh ephemeris, when saidnavigation satellite system receiver subsequently transitions from saidstandby mode to a normal mode of operation.
 13. The system according toclaim 12, wherein said one or more circuits are operable to enabletransition from said wakeup state back to said sleep state in saidstandby mode, subsequent to said acquisition of said fresh ephemeris.14. The system according to claim 12, wherein said fresh ephemeris isacquired from GPS signals, GLONASS signals, and/or Galileo signals. 15.The system according to claim 12, wherein said one or more circuits areoperable to store said acquired fresh ephemeris in said navigationsatellite system receiver.
 16. The system according to claim 12, whereinsaid one or more circuits are operable to return to said sleep state insaid standby mode from said normal mode of operation.
 17. The systemaccording to claim 12, wherein said one or more circuits are operable toreturn to said wakeup state in said standby mode from said normal modeof operation.
 18. The system according to claim 12, wherein said one ormore circuits are operable to stay in said normal mode of operationafter said transition from said standby mode to a normal mode ofoperation.
 19. The system according to claim 12, wherein, for saidstandby mode, a sleep period of said sleep state and a wakeup period ofsaid wakeup state are predetermined or dynamically adjusted.
 20. Thesystem according to claim 19, wherein said sleep period of said sleepstate and said wakeup period of said wakeup state are determined basedon QoS, quality of said acquired fresh ephemeris, and/or user inputs.21. The system according to claim 19, wherein said sleep period of saidsleep state is less than a period at which said fresh ephemeris ischanged by one or more satellites.
 22. The system according to claim 19,wherein said wakeup period of said wakeup state is greater than or equalto a period required for collection of said fresh ephemeris.